PHP Fatal error

Hi guys,

This ticket is a request for you to introduce a change described below, to avoid an PHP Fatal error: Uncaught Error: Call to a member function enqueue() on null that a site with this plugin enabled was experiencing and needed fixing.

There are a few threads going around reporting the same error, with replies mostly being that you are not able to reproduce.

With this site, I could reproduce it, and I think I have figured it out.

FYI, the error happens when trying to Add or Edit Pages from the backend specifically, and results in a WSOD and users completely unable to access their existing Pages or adding New Pages when this plugin is enabled.

This is what I have tracked it down to:

In the file sensei-certificates\classes\class-woothemes-sensei-certificates.php, on lines 109 to 111 in you have this code:

if ( class_exists( 'Sensei_Assets' ) ) {
	$instance->assets = new \Sensei_Assets( $instance->plugin_url, dirname( __DIR__ ), SENSEI_CERTIFICATES_VERSION );
}

This ends up causing the Fatal Error on sites that have older versions of Sensei, where the class Sensei_Assets does not exist, and $instance->assets is left undefined, as there is no else setting it.

When in the function enqueue_block_editor_assets this code attempts calling it like so

WooThemes_Sensei_Certificates::instance()->assets->enqueue(
 'sensei-certificates-block',
 'blocks/index.js'
);

This results in Fatal Error:

PHP Fatal error:  Uncaught Error: Call to a member function enqueue() on null in path-to-site\wp-content\plugins\sensei-certificates\classes\class-woothemes-sensei-certificates.php:1472
Stack trace:
#0 path-to-site\wp-includes\class-wp-hook.php(307): WooThemes_Sensei_Certificates->enqueue_block_editor_assets('')
#1 path-to-site\wp-includes\class-wp-hook.php(331): WP_Hook->apply_filters(NULL, Array)
#2 path-to-site\wp-includes\plugin.php(474): WP_Hook->do_action(Array)
#3 path-to-site\wp-admin\edit-form-blocks.php(265): do_action('enqueue_block_e...')
#4 path-to-site\wp-admin\post-new.php(72): require('C:\\wamp74\\www\\s...')
#5 {main}
  thrown in path-to-site\wp-content\plugins\sensei-certificates\classes\class-woothemes-sensei-certificates.php on line 1472

A possible fix, which you can apply as is to at least prevent a Fatal Error that brings down sites entirely, is to update the function to check the assets are set and bail early if they are not like so

**
 * Enqueue block assets for the editing interface.
 *
 * @access private
 */
public function enqueue_block_editor_assets() {
  $screen = get_current_screen();

  if( !WooThemes_Sensei_Certificates::instance()->assets ){
      return;
  }

  if ( $screen && 'page' === $screen->post_type ) { 
   WooThemes_Sensei_Certificates::instance()->assets->enqueue(
   'sensei-certificates-block',
   'blocks/index.js'
  );
  }
 }

Granted, this I imagine from scanning the code quickly would leave the Certificates block unavailable in the Block Editor, but it definitely beats a server error, no?

If you could please let me know if it will be possible for you to incorporate this change, would greatly appreciate it.

Any questions, happy to help.